I have a situation:
> qsub -l nodes=6:ppn=2 /path/to/mpi_program
where "mpi_program" is:
/path/to/mpirun -np 12 /path/to/my_program
-- Everything went to run on head node (one time on the first compute node). Jobs can be done anyway.
While the mpirun can run on its own by specifying a "-machinefile", it is pointed out by Glen, and also on this web site http://wiki.hpc.ufl.edu/index.php/Common_Problems that it's not a good idea to provide machinefile since it's "already handled by OpenMPI and Torque".
But in my case why the OpenMPI and Torque is not handling the jobs to nodes?
Zhiliang